perf(18/2024): optimize by pre-allocation memory for collections

manhunto · Dec 20, 2024 · 2282c0c · 2282c0c
1 parent 5165099
commit 2282c0c
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Showing 2 changed files with 11 additions and 4 deletions.
diff --git a/readme.md b/readme.md
@@ -28,7 +28,7 @@
 | [Day 15: Warehouse Woes](src/solutions/year2024/day15.rs)         |   ⭐⭐   |            7.226 |            9.084 |
 | [Day 16: Reindeer Maze](src/solutions/year2024/day16.rs)          |   ⭐    |            6.478 |                - |
 | [Day 17: Chronospatial Computer](src/solutions/year2024/day17.rs) |   -    |                - |                - |
-| [Day 18: RAM Run](src/solutions/year2024/day18.rs)                |   ⭐⭐   |            2.487 |          379.772 |
+| [Day 18: RAM Run](src/solutions/year2024/day18.rs)                |   ⭐⭐   |            2.487 |          204.885 |
 | [Day 19: Linen Layout](src/solutions/year2024/day19.rs)           |   ⭐⭐   |            2.923 |           22.751 |
 
 # 2023

diff --git a/src/solutions/year2024/day18.rs b/src/solutions/year2024/day18.rs
@@ -45,12 +45,16 @@ impl Solution for Day18 {
         let start = self.surface.top_left_corner();
         let end = self.surface.bottom_right_corner();
 
-        let mut skipped: HashSet<Point> = byte_positions
+        let mut skipped = HashSet::with_capacity(byte_positions.len());
+
+        let new: HashSet<Point> = byte_positions
             .clone()
             .into_iter()
             .take(self.memory_size)
             .collect();
 
+        skipped.extend(new);
+
         #[allow(clippy::needless_range_loop)]
         for i in self.memory_size..byte_positions.len() {
             let current = byte_positions[i];
@@ -80,8 +84,11 @@ impl Day18 {
     }
 
     fn is_reachable(&self, blocked: &HashSet<Point>, start: Point, end: Point) -> bool {
-        let mut visited = HashSet::new();
-        let mut queue = vec![start];
+        let mut visited = HashSet::with_capacity(self.surface.area());
+        let mut queue = Vec::with_capacity(self.surface.area());
+
+        queue.push(start);
+        visited.insert(start);
 
         while let Some(current) = queue.pop() {
             if current == end {